Its hero Ulrich von Bek is a mercenary and freethinker, who finds himself a damned soul in a castle owned by Lucifer.
Much to his surprise, von Bek is charged by Lucifer with doing God's work, by finding the Holy Grail, the "cure for the world's pain", that will also cure Lucifer's pain by reconciling him with God.
After many adventures, von Bek eventually finds the Holy Grail, and discovers that it will set mankind on the path to self-redemption through rationality, without the help of God or the hindrance of Lucifer.
Dave Pringle reviewed The War Hound and the World's Pain for Imagine magazine: "I am pleased to report that it makes a delightful read.
It is much superior to the earlier quickies in, say, the 'Dorian Hawkmoon' series, Moorcock has honed his skills over the years, and they now show a fine gleaming edge".